Re-emergence of monkeypox in Africa: a review of the past six years

Abstract

Human monkeypox was first identified in 1970 in the Democratic Republic of the Congo. Extensive studies of this zoonotic infection in the 1970s and 1980s indicated a largely sporadic disease with a minority of cases resulting from person-to-person transmission, rarely beyond two generations. In August 1996, an unusually large outbreak of human monkeypox was reported, and cases continued through 1997 with peak incidence in August 1996, March 1997 and August 1997. Preliminary results from the field investigations in 1997 suggest a new epidemiological pattern where a majority of secondary cases result from person-to-person transmission, and a clinically milder disease. But there is preliminary laboratory evidence of a simultaneous outbreak of varicella in the same geographic region which will undoubtedly modify these preliminary results. Since smallpox was eradicated and vaccinia vaccination terminated in this region, the population of susceptible individuals has grown. The use of vaccination to protect the population at risk, however, must take into account HIV prevalence and the risk of generalized vaccinia when using vaccinia vaccine in populations where HIV is known to be present.

The Pathology of Experimental Aerosolized Monkeypox Virus Infection in Cynomolgus Monkeys (Macaca fascicularis)

“…Secondary transmission accounted for 24% of 103 cases surveyed from 1984 to 1986 (Marennikova et al, 1989). Previous estimates of the secondary attack rate for monkeypox among susceptible contacts range from as low as 3.3% to as high as 15% (Arita et al, 1985;Breman et al, 1977Breman et al, , 1980Heymann et al, 1998), compared with the 25% to 45% secondary attack rate for smallpox (Breman et al, 1977(Breman et al, , 1980. The low rate of secondary transmission may have limited the opportunity for sustained monkeypox infection among humans, and the disease occurred as self-limiting outbreaks of sporadic incidence.…”

“…The low rate of secondary transmission may have limited the opportunity for sustained monkeypox infection among humans, and the disease occurred as self-limiting outbreaks of sporadic incidence. Current evidence, however, suggests an increased risk for secondary person-to-person transmission (Anonymous, 1997a(Anonymous, , 1997b(Anonymous, , 1998Cohen, 1997;Heymann et al, 1998;Mukinda et al, 1997). The most recent outbreak of monkeypox in the Democratic Republic of the Congo (former Zaire) was the largest cluster of human monkeypox cases ever reported.…”

“…With the eradication of smallpox and widespread discontinuation of vaccinia vaccination, monkeypox has re-emerged as a human health threat (Anonymous, 1997a(Anonymous, , 1997c(Anonymous, , 1998Arita et al, 1985;Cohen, 1997;Heymann et al, 1998;Mukinda et al, 1997). Although vaccinia vaccination protects against monkeypox, the risk of adverse effects warrants careful consideration before the vaccine is reintroduced into a population that may be immunocompromised because of a high incidence of HIV infection (Anonymous, 1997a(Anonymous, , 1997cHeymann et al, 1998;McConnell et al, 1964).…”

“…Although vaccinia vaccination protects against monkeypox, the risk of adverse effects warrants careful consideration before the vaccine is reintroduced into a population that may be immunocompromised because of a high incidence of HIV infection (Anonymous, 1997a(Anonymous, , 1997cHeymann et al, 1998;McConnell et al, 1964).…”

When good vaccines go wild: Feral Orthopoxvirus in developing countries and beyond

“…After the eradication of smallpox, monkeypox became the most important orthopoxvirus to infect humans [43,94,[126][127][128][129]. Human cases of monkeypox, however, were rare events since only a few confirmed cases were reported during the 1970s.…”